1. Technical Field
The present invention relates to a cathode ray tube (CRT), and more particularly, to a cathode ray tube with a structure for preventing electron beam mis-landing caused by geomagnetism.
2. Related Art
Generally, a cathode ray tube is designed to realize an image by scanning a phosphor screen deposited with red R, green G, and blue B phosphors with electron-beams emitted from an electron gun. The electron beams are deflected by a deflection yoke and landed on desired corresponding phosphors to scan the peripheral portion of the phosphor screen as well as the central portion.
However, when the electron beams are deflected, they are affected by external magnetic fields such as that caused by geomagnetism, which causes the electron beams to land on undesired phosphors. This is called mis-landing, and it deteriorates color purity of the cathode ray tube.
To solve the above problem, a magnetic field shield member such as an inner shield for shielding the electron beams from the geomagnetism can be employed. The inner shield is generally mounted on a color selection apparatus disposed inside the cathode ray tube and includes a shadow mask and a mask frame.
In recent years, a flat, large-sized screen panel has been developed to improve the definition of an image realized at a peripheral portion of a large-sized screen. Accordingly, the color selection apparatus employed to realize colors in the cathode ray tube has also been flattened and increased in size so that it can be properly associated with the flat screen panel.
A color selection apparatus comprises a mask provided with plural electron-beam passing apertures and a frame for supporting the mask applied with a predetermined tension. The frame comprises a pair of U-shaped elastic members and a pair of supporting members coupled to the elastic members, the shadow mask being tensioned and mounted on the supporting members.
Due to the space between the elastic members and the shadow mask, a geomagnetism component can adversely affect the electron beams passing through the apertures. This causes the electron beams to land on undesired phosphors, deteriorating the color purity of the cathode ray tube.
Therefore, the present invention has been made in an effort to solve the above-described problems. It is an objective of the present invention to provide a cathode ray tube that is designed to minimize affection by the east-west (E-W) geomagnetic component of the geomagnetism thereon, thereby improving the color purity of the cathode ray tube by enhancing the beam landing accuracy.
To achieve the above objectives and others, the present invention provides a cathode ray tube, comprising: a panel having a front screen portion on which a phosphor screen is formed, and a panel flange integrally formed on an edge of the front screen portion; a funnel connected to the panel flange; a deflection yoke disposed around the funnel; a neck connected to the funnel; an electron gun disposed in the neck; a color selection apparatus for selecting electron beams emitted from the electron gun and allowing the selected electron beams to land on corresponding phosphors; and an inner shield for shielding geomagnetism, the inner shield mounted on the color selection apparatus; wherein the color selection apparatus comprises a mask having a plurality of electron beam-passing apertures, the mask being rectangular and having a longitudinal axis and a lateral axis, a frame for supporting the mask in a tensioned state, and a pair of side shield members mounted on lateral sides of the frame to shield the geomagnetism.
Preferably, the side shield members have a magnetic permeability higher than that of the inner shield. The frame comprises a pair of supporting members disposed at a predetermined distance from each other in parallel, and a pair of elastic members fixed on both ends of the supporting members to correspond to the lateral sides of the mask.
Preferably, the side shield members are formed of a material having a magnetic permeability above 400 within a magnetic field having a magnetic flux density of about 0.35 gauss (G).
The side shield members are fixed on the elastic members while blocking a space defined between the mask and the elastic members and further fixed on the supporting members.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a cathode ray tube, comprising: a panel having a front screen portion and a phosphor screen, said panel having a panel flange integrally formed on an edge of the front screen portion; a funnel connected to the panel flange; a deflection yoke disposed around said funnel; a neck connected to said funnel; an electron gun disposed in said neck; a color selection apparatus for selecting electron beams emitted from said electron gun, the selected electron beams landing on phosphors of the phosphor screen; and an inner shield shielding geomagnetism, said inner shield being mounted on said color selection apparatus. The color selection apparatus comprises: a mask forming a plurality of electron beam-passing apertures, said mask being rectangular and having a longitudinal axis and a lateral axis; a frame supporting said mask in a tensioned state; and a pair of side shield members shielding geomagnetism, said side shield members being mounted on lateral sides of said frame.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus, comprising: an inner shield for shielding geomagnetism; and a color selection unit for selecting electron beams emitted from an electron gun, the selected electron beams landing on phosphors of a phosphor screen, said inner shield being mounted on said color selection unit. The color selection unit comprises a mask forming a plurality of electron beam-passing apertures, a frame for supporting said mask in a tensioned state, and a pair of side shield members shielding geomagnetism, said side shield members being mounted on opposite sides of said frame.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus, comprising: an inner shield for shielding geomagnetism; a color selection unit for selecting electron beams emitted from an electron gun, the selected electron beams landing on phosphors of a phosphor screen, said inner shield being mounted on said color selection unit. The color selection unit comprises: a mask having a face region forming a plurality of electron beam-passing apertures; a frame for supporting said mask in a tensioned state, said frame having two longitudinal sides opposite each other, said frame having two lateral sides opposite each other, the longitudinal sides being longer than the lateral sides; and a pair of side shield members for shielding geomagnetism, said side shield members being mounted at the lateral sides of said frame.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example. Other advantages and features will become apparent from the following description and from the claims.